A cubic box with sides of 20.0 cm contains 2.00×1023 molecules of helium with a root-mean-square speed (thermal speed) of 200 m/s. The mass of a helium molecule is 3.40×10−27 kg. What is the average pressure exerted by the molecules on the walls of the container? The Boltzmann constant is 1.38×10−23 J/K and the ideal gas constant is R=8.314 J/mol K = 0.0821 L atm/mol K.
(a) 3.39 kPa
(b) 1.13 kPa
(c) 570 Pa
(d) 2.26 kPa